QI-FRET: a new tool in Receptor Tyrosine Kinase research Kalina Hristova, Johns Hopkins University Ligand-independent homo and heterodimerization of receptor tyrosine kinases (RTKs) is a process that is not well understood despite being implicated in various human pathologies. The lack of knowledge is mainly due to a lack of an appropriate methodology to measure the dimerization energetics of full-length RTK. The lack of knowledge is, in turn, a bottleneck in developing effective RTK-targeted therapies. Here we propose to (i) develop a quantitative imaging FRET (QI-FRET) method that yields dimerization free energies in plasma membrane-derived vesicles and to (ii) characterize the homo and heterodimerization free energies of the ErbB and FGF receptors, chosen because of their very strong link to human disease. Upon the completion of this work, we will be able to predict the degree of ligand-independent dimerization, and thus biological activity, as a function of RTK expression. The method that will be established and the knowledge gained will ultimately aid the search and refinement of effective RTK-targeted treatments for cancers and growth disorders.